Even without firm proof that a bomb brought down a Russian airliner over Egypt nearly two weeks ago, airline officials around the world are demanding better security at airports to prevent terrorists from gaining access to planes.

With both the Russian and British government suspending flights to Sharm el Sheikh, the resort where the A321 took off, we could be entering a new era where airlines either selectively impose additional security at airports—much as Israel's flag carrier El Al does almost everywhere it flies—or cease operations until upgrades are made. Russia, in fact, has gone further than the U.K. and is banning all flights to Egypt. The U.S. doesn’t have as much direct service to the region, but Homeland Security Secretary Jeh Johnson said that security will be enhanced at up to ten airports in the Middle East with nonstop flights to the U.S., including Cairo, Amman, and Kuwait City.

EasyJet CEO Carolyn McCall, whose airline brought back stranded British tourists from the Red Sea resort, said the attack has put a spotlight on airports where security isn’t up to international standards. Emphasizing that some international airports “do this very well,” she said the focus should be on “certain airports” deemed more vulnerable, either due to their location or to the state of their security apparatus. The bomb scenario, she said, is the one “that keeps airline executives awake at night,” she told the BBC.

Among the key reforms that security experts are demanding is a more thorough vetting of airport workers with access to secure areas; improved explosives-detection technology, and more frequent inspections by outside auditors. In fact, the International Civil Aviation Organization sent in a multi-national team of aviation experts to check out Cairo’s security right after the recent crash. Meanwhile, investigators are continuing to examine all possibilities—including a technical failure—for what downed Metrojet Flight 9268; the crash, which killed all 224 aboard, is the worst civil aviation accident in Russian history. Sources close to the investigation say that the bomb theory advanced further after the release of the cockpit voice recording. A loud noise captured in the final moments of the flight was likely caused by explosives rather than a mechanical problem, experts said. Mary Schiavo, former DOT inspector general and now an attorney in private practice, said that the ability to analyze such noises has improved dramatically since the bombing of Pan Am Flight 103 over Lockerbie, Scotland, in 1988; that case took several years to solve. "There’s a great database now and they can analyze sound and compare it with other sounds from previous investigations," she said.

But confirming it was a bomb is just one part of the puzzle: The question for airport security is who planted it. Was it brought aboard by a passenger or planted on the plane by an airport worker? At many airports, employees don’t have to pass through the same screening that passengers do—although in the U.S. the TSA routinely performs spot checks.